Inlet level control for papermaking machine



Sept. 4, 1956 L. HORNBOSTEL INLET LEVEL CONTROL FOR PAPERMAKING MACHINE Filed March 11, 1954 V 2 Sheets-Shoot 1 United States Patent F INLET LEVEL CGNTROL FGR PAPERMAKDIG MA'Cim Lloyd Hornbostel, Beloit, Wis, assignor to Beloit iron Works, Beloit, Wis, a corporation of Wisconsin Application March 11, 1954, Serial No. 415,565 6 Claims. (CI. 92-43) The instant invention relates to an improved stock flow system for a paper machine, and more particularly, to an improved method and means for flowing stock in 2. cylinder machine.

In a cylinder paper machine, the cylinder mold is suitably mounted for rotation in a vat which holds the stock at a predetermined level. The cylinder mold has :a perforate forming surface, which may or may not be covered, so as to provide a suitable forming surface against which the stock in the vat may be drawn to deposit a fibrous Web thereon and pull white water therethrough into the inside of the cylinder. The cylinder is rotated and the fibrous Web adhering to the uprunning side of the cylinder is taken off from the cylinder mold surface by suitable felt carriers. The white water which is drawn through the cylinder mold surface has a relatively low fiber content in the neighborhood of 0.0l0.l% (e. g. 0.02% normally). In contrast, the stock in the vat has a substantially higher fiber content, of at least about 0.2% (e. g. 0.25% normally). Maintenance of a constant desired stock level in the vat is of critical importance in the operation of the cylinder mold; and this has been done heretofore by means of fiow control device in the feed line to the vat, which operates in response to the desired level in the vat. Such flow control device, of course, regulates the flow of the relatively high consistency stock by a valve or similar control device. Stock of any appreciable consistency, as contrasted to the white water, is often rather difficult to handle.

In contrast, the instant invention provides a novel control device and procedure whereby the relatively easily handled white water is employed in order to obtain the "fine level control required and the level in the vat is maintained constant by the use of level control means in the flow box that are responsive to the level of the stock in the vat.

it is, therefore, an important object of the instant invention to provide an improved method and apparatus for eflfecting controlled stock flow in a paper machine, and more particularly, for effecting stool: level control in the vat of a cylinder mold machine.

Another important object of the instant invention is to provide an improved method for controlling the stock level in a cylinder mold vat which comprises the steps of (a) diluting stuif with white water to obtain stock of substantially the desired consistency for forming paper on the cylinder mold, (b) flowing such stock from a flow box to the vat to continuously maintain stock in the vat at a given level, (0) withdrawing white water from within the cylinder in the vat, (d) recirculating a substantial proportion of the withdrawn white water back to efiect the dilution of the stuff in step (a), and (e) flowing an additional portion of the withdrawn white water directly into the how box at a rate responsive to the stock level in the vet, whereby a constant desired level of stock may be maintained in the vat.

A further object of the instant invention is to provide a stock flow system for a cylinder machine, that com- Patented Sept. 4, 1956 prises a cylinder mold, a vat mounting the mold and adapted to receive stock for forming a paper web on the mold, a flow box having stock therein, conduit means responsive to the stock level in the flow box flowing stock from the flow box to the vat, draw-off means communicating with the cylinder mold interior withdrawing white water therefrom, and second conduit means responsive to the stock level in the vat communicating with said drawoff means to how white water into said flow box at a rate sufiicient to maintain a constant level in the vat.

Other objects, features and advantages of the instant invention will become apparent to those skilled in the art from the following detailed description thereof and the accompanying drawings which are made a part hereof.

On the drawings:

Figure l is a diagrammatical view showing the stock flow system of the instant invention;

Figure 2 is a flow sheet showing a stock flow system embodying the instant invention; and

Figure 3 is another flow diagram showing a stock flow system embodying the instant invention.

As shown on the drawings:

In Figure l, the reference numeral 10 indicates generally the stock flow system embodying the instant invention. In the instant system 10 an initial phase in the preparation of stock for use in the cylinder machine designated generally by the reference numeral 1, is the beating treatment which is followed by the refining treatment. The most common type of refining engine is the Jordan engine which is named after its inventor and which is usually referred to merely as a Jordan. The Jordan 12 takes its supply of the beater product from a chest (not shown) continuously, for example, at the conduit 12a and eifects refining of the stuff by a type of centrifugal beating action. The material produced by the heater and refined by the Jordan 12 is referred to in the art as stud and may have a consistency of about 24% (i. e., the air dry Weight per cent of fibers suspended in the aqueous medium). The stuff flows from the Jordan 12 through a conduit 13 and into the stuff chest 14, which acts as a reservoir. In Figure 1, the flow of stuif and stock is usually shown as gravity flow, and this would be preferred in most instances, although pumps may be used to move this material. A controlled amount of stuff is caused to flow continuously from the stuff chest 14 through the conduit 15 and into the regulating box 16, whereat the stuif is diluted by the addition of white water through the conduit 17.

In the instant system it the regulator 16 functions to accomplish the initial dilution of the stuff to provide stock which is ultimately diluted to a slightly greater extent. In the paper machine art, the stock is generally considered to be the material which has approximately the consistency that will ultimately be used at the forming surface, which in this case is in the cylinder machine 11. It will thus be seen that the stuif generally has a consistency of about 24%, the stock generally has a consistency of about 0.1% to perhaps 0.75%, and the white water has a consistency of 0.01-0.1%. Because of the rather substantial differences in flow characteristics among the stud, stock and white water, these materials :are considered in the art to be substantially different, particularly for purposes of handling in the stock flow system.

The source for the white water flowing in the conduit 17 will be described hereinafter, but it will be noted that a control valve 18 is mounted in the conduit 17 in order to control the amount of white water flowing into the regulating box 16. The stuff entering through the conduit 15 and the white water entering through the conduit 17 are both introduced into the regulating box 16 in predetermined amounts so as to obtain a desired quantity of stock having a desired predetermined consistency. As indicated in the flow sheets of Figures 2 and 3, wherein G indicates a volume unit of material, about 1 volume of stuff of 3% consistency is admixed with about 4.8 volumes of white water (W. W.) of 0.03% consistency in the regulating box (Reg. Box) 16 in order to obtain a total of 5.8 volume units of stock of about 0.55% consistency.

The stock is next transferred through the conduit 19 and into the screen system 20 which may include rifilers or sandtraps as well as the screens 20, here indicated. The screen showers (not shown) introduce about 0.5 volume of water into the system, thereby providing 6.3 volumes of stock of 0.5% consistency at the screen exit. The purpose of the screens is that of removing as much as possible of the dirt, slivers, etc., which may have accumulated in the stock. From the screens 20 the stock is flowed through the conduit 21 and into the flow box 22.

The flow box functions in a number of different types of paper machines and is sometimes referred to as the head box or the breast roll feed box (in the case of Fourdrinier type machines), although the functions of the flow box in each of these difierent types of machines are not necessarily the same. In the cylinder machine of the present invention, the flow box 22 carries out a plurality of functions, all of which are important to the effective operation of the instant machine. One of the principal functions of the flow box 22 is that of accomplishing the final dilution of the stock to obtain the consistency desired for use in the cylinder machine 11, which is approximately 0.2%. The consistency of 0.2% is accomplished primarily by dilution of the 0.5% stock coming from the screens 20 with white water coming from the conduit 23, having a control valve 24 therein. As indicated in the flow sheets of Figures 2 and 3, approximately 8.8 volume units of white water are added through the conduit 23 to the approximately 6.3 volume units of 0.5 stock flowing through the conduit 21 and into the flow box 22.

As will be explained hereinafter, the amount of white water which enters the flow box 22 through the conduit 25 is so small (e. g. about 0.2 volume) that the consistency of the stock in the flow box 22 is not appreciably afiected.

The stock in the head box 22 is permitted to flow by gravity through the bottom outlet at 26 and the conduit 27 communicating therewith downwardly through a horizontal reach 27a of the conduit and then from beneath the cylinder machine 11 upwardly through a vertical reach 27b of the conduit and into the vat 28 of the cylinder machine 11. The vat 28 has a generally semi-cylindrical bottom 28a which conforms generally to the cylindrical contour of the cylinder mold itself 29. The stock flows upwardly through the vertical reach 27b of the conduit 27 to approximately the level L of the stock in the vat 28 and then over a baffle-like wall portion 28b of the vat 28 (and preferably through a rectifier roll or flow evener 30) in order to flow into the vat proper defined by the curved bottom portion 28a. A total of about 15.3 volumes of 0.2% stock flows into the vat 28.

In the operation of the cylinder machine 11, the cylinder drum 29 is rotated counter-clockwise (as here shown). The drum 29 is formed with a perforate surface such as the Fourdrinier forming wire, which permits water to pass therethrough but which builds up the stock fibers on the outer surface. Accordingly, a web W is built up on the outer surface of the drum 29 and this web W rises above the stock level L on the uprunning side of the drum 29 and is brought into contact with a pick-up felt F pressed against the drum 29 by a couch roll 31, whereby the web is elfectively transferred to the bottom side of the felt F. This operation is fully understood by those skilled in the art and need not be further discussed herein. It will be appreciated, however, that the speed of rotation of the drum 29 and the stock level L must be very closely correlated so that a uniform web deposit will be obtained on the surface of the drum 29. If, for example, the stock level were to rise somewhat during operation, then the total amount of head which would be available for web buildup during the submerged travel of the drum 29 would be increased and the web thickness would be correspondingly increased. Fluctuations in the web thickness or weight cannot, of course, be tolerated in commercial production of uniform types of paper. For this reason, it is particularly important to control the stock level L in the operation of the cylinder machine 11. Heretofore, the stock level L had been controlled merely by a valve in the conduit 27 that was actuated by a level sensing device in the vat 28. This involved valve control of a stock stream, wherein the relatively high concentration of fibers tended to interfere with the proper functioning of the valve.

In the instant invention, however, no such level control is employed in the vat 28 and there is no extra handling of the stock flowing into the vat 28 through the conduit 27, once it has been adjusted to the proper consistency and cause to start into the vat 28. Instead, the level L of the stock in the vat 28 is maintained constant by flowing controlled amounts of white water into the flow box 22 in response to fluctuations in the vat level L. White water in smallcontrolled amounts is flowed into the flow box 22 by a valve 32 operated in response to a level sensing device 33 in the vat 28. It will be appreciated that by the use of a conduit 27 which is of sufficient size to reduce friction losses therein to a negligible consideration it is possible to operate so that the level L which is maintained in the flow box 22 completely controls the level L which is maintained in the vat 28. It will also be appreciated that it is possible to use means other than the conduit 27 which are responsive to the stock level L' in the flow box 22 for flowing stock from the flow box 22 to the vat 28. These means might include a controlled pump (not shown) or a definite restriction in the conduit 27 (also not shown) which eflfected a predetermined friction loss in the conduit 27 so that the flow box 22 and the vat 28 might be maintained at substantially different levels. However, it has been found that gravity flow (with or without the use of pressure at the top of the flow box 22) is preferable for use in the practice of the invention.

Referring now to the white water system here employed, it will be noted that the white water W. W. collects within the drum 29 at a level L that is somewhat lower than the level L of the stock in the vat 28. The level L" of the white water within the drum 29 is maintained by means of a suitable overflow device 34 which flows into a chest or reservoir 35 in the White water system. The chest 35 is provided with an overflow 36 which may flow white water to the save-alls (not shown) or a sewer. As will be appreciated, the stuff entering the instant stock flow system 10 has a consistency of only about 3%, whereas the web W departing from the instant system 10 on the drum 29 has a consistency of perhaps 12%. There is thus a substantially greater amount of water introduced into the system 10 than there is taken out. As indicated in the flow sheets of Figures 2 and 3, this volume of water may be approximately 3 volumes (1. e. 3.16) as compared with an initial 1 volume of stuff (plus the fresh water F. W. added through the showers etc.) entering into the system 10. In order to successfully operate the cylinder drum 29 this water must be removed and put into some other system (not shown) and this is accomplished by means of the overflow level control device 36. It will be appreciated that the device 36 is represented only diagrammatically in the instant drawing, since its operation is well understood by those skilled in the art and need not be described in detail herein. In essence, the overflow pipe 34 extends from the level L" within the drum 29 through a hollow axle 0r trunnion portion (of the drum 29) and then downwardly to the white water chest35 (all of which structure is well known in the art and not shown herein).

All of the white water which collects within the chest 35 is not drawn off by the overflow device 36, however, since a substantial proportion of this white water may be reused in the instant flow system 10. Accordingly, a second drawoif means or conduit 37 is mounted on the chest 35 and extends into the suction side of a fan pump P. As previously mentioned, the structure required for drawing off liquid from within the drum 29 is fully understood by those skilled in the art and the instant drawoff means 37 differs from the overflow drawofi means 36 only in that its opening within the chest 35 is below the white water level therein.

The white water in the conduit 37 is drawn into the suction side of the fan pump P. From the fan pump P the white Water is discharged into a main header 38, which accommodates a relatively large volume of white Water flow, this being indicated in the flow sheets of Figures 2 and 3 as being approximately 13.7 volumes per volume of stuif entering the system through the conduit 15 from the stuff chest 14. The white water conduits 17 and 23 communicate with the header 38 and are also adapted to accommodate a rather substantial amount of flow. As indicated in the flow sheets of Figures 2 and 3, the conduit 17 leading to the regulating box 16 feeds about 4.8 volumes of white water thereto for each volume of stuff entering the regulating box, and the white water conduit 23 feeds about 8.8 volumes of white water into the flow box 22 for each volume of stulf entering the system 10. In actual practice, the regulating box 16 and the flow box 22 are relatively small compared to the volume of material handled thereby in a given time interval. Since the total volume of all of the containers and reservoirs handling stock, which include the regulating box 16, the screens 20, the flow box 22 and the conduits extending therebetween, have a rather appreciable total volume; it will be appreciated that slight fluctuations in the fan pump P output will not reflect drastic changes in the consistency throughout the system. Better consistcncy control is also obtained by the use of more than one white water mixing station, as here shown the mixing stations being at the regulating box 16 and again at the flow box 22.

The instant invention provides conduit means indicated generally at 25 which communicate with the fan pump output at the header 34 and which are effective to cause the white water to flow into the body of stock in the flow box 22 at a rate sufficient to maintain a constant desired level L in the stock body in the vat 28. It will be noted that the conduit 25 communicates with the header 34 immediately adjacent the discharge of the fan pump P and before the conduits 23 and 17 communicate with the header 34. This gives the conduit 25 the maximum operating pressure and, therefore, the most rapid action possible.

The conduit 25 has mounted therein a valve 32 which effectively controls the flow of white water through the conduit 25. The valve 32 is controlled by means 33 responsive to the vat level L, which means 33 are here shown as a float actuated control, comprising a float 33a which floats on the stock and moves upwardly and downwardly with fluctuations in the vat level L, an actuating arm 33b which interconnects the float 33a and a control box 33c and electric lead lines 33d connecting the control box 330 with the valve control 33c directly connected to the stem of the valve 32 for opening and closing the valve 32 in response to movement of the float 33a. Other level control devices may be used to actuate the valve 32, if desired. The important thing is that the operation of the valve 32 is controlled by the particular location of the vat stock level L. As soon as the level L starts to fall, it is brought back up to the desired position by the flow of white water through the valve 32. The relatively small amount of white Water which is involved in the operation of the level control conduit 32 has little or no' appreciable eflect upon the stock consistency in the system. As indicated in the flow sheets of Figures 2 and 3, if the average amount of white water addition through the conduit 25 is even as great as A of a volume unit of stufi entering the system (on an equal unit of time basis) the decrease in stock consistency thus reflected is in the neighborhood of 0.002%, which is clearly negligible.

As is indicated, the conduit means 25 responsive to the level L in the vat 23 is preferably separate and apart from the main white water conduit 23 feeding into the flow box 22, for the reason that sharper control can be obtained when the relatively small volume of white water handled by the conduit 25 is employed; and sharp fluctuations in the fan pump output can be corrected instantly by the use of the conduit means 25 positionednearest the fan pump discharge.

In completing the Water balance shown in Figure 3, it will be noted that the web W on the wire (about 0.246 volume units of 12% consistency) is first pressed to obtain a drier web (about 0.084 volume units of 35% consistency) and then dried to obtain the final web (about 0.031 volume units of 94% consistency).

It will be understood that modifications and variations may be effected without departing from the scope of the novel. concepts of the present invention.

I claim as my invention:

1. In the art of controlling the stock level in a cylinder mold vat in a paper machine, the improvement which comprises the steps of (a) diluting stufi with white Water in a regulating box in the machine to obtain stock of slightly greater consistency than desired for use in the vat, (b) flowing the stock of step (a) from the regulating box to a flow box and therein diluting the stock with white water to obtain substantially the desired consistency for use in the vat, (c) flowing the stock of step (b) from the flow box to the vat to continuously maintain stock in the vat at a desired level, (d) withdrawing white water from within the cylinder in the vat, (e) recirculating a substantial proportion of the withdrawn white water back to effect the dilution of the stuff in steps (a) and (b), and (f) flowing an additional portion of the withdrawn White water separate and apart from the white water used in step (d) directly into the flow box at a rate responsive to the stock level in the vat.

2. In a paper machine stock flow system for a cylinder machine, a cylinder mold, a vat mounting the mold and adapted to receive stock for forming a paper web on the mold, a flow box having stock therein, conduit means responsive to the stock level in the flow box flowing stock from the flow box to the vat, draw-oil means communicating with the cylinder mold interior Withdrawing white water therefrom and communicating with said flow box to flow white water thereinto, stock level sensing means in the vat, and valve means responsive to the stock level sensing means in the vat and in control of white Water flow through said draw-01f means into the flow box.

3. In a paper machine stock flow system for a cylinder machine, a cylinder mold, a vat mounting the mold and adapted to receive stock for forming a paper web on the mold, a flow box, first conduit means flowing stock into said flow box, second conduit means flowing white Water into said flow box to dilute the stock therein, third conduit means flowing stock from the flow box to the vat, drawofl means communicating with the cylinder mold interior withdrawing white water therefrom and communicating with said second conduit means, and fourth conduit means responsive to the stock level in the vat communicating with said draw-off means to flow white Water into said flow box at a rate sufiicient to maintain a constant level in the vat.

4. In a paper machine stock flow system for a cylinder machine, a cylinder mold, a vat mounting the mold and adapted to receive stock for forming a paper web on the mold, a flow box, first conduit means flowing stock into said flow box, second conduit means flowing white water into said flow box to dilute the stock therein, third conduit means flowing stock from the flow box to the vat, draw-off ,means communicating with the cylinder mold interior withdrawing white water therefrom and communicating with said second conduit means, fourth conduit means afiording communication between said flow box and said draw-0E means, and valve means responsive to the stock level in said vat in control of stock flow through said fourth conduit means.

5. In a paper machine stock flow system for a cylinder machine, a cylinder mold, a vat mounting the mold and adapted to receive stock for forming a paper web on the mold, a flow box, first conduit means flowing stock into said flow box, second conduit means flowing white water into said flow box to dilute the stock therein, third conduit means flowing stock from the flow box to the vat, drawoif means communicating with the cylinder mold interior withdrawing white water therefrom and communicating with said second conduit means, fourth conduit means affording communication between said flow box and said draw-01f means, valve means in said fourth conduit means in control of stock flow therethrough, and means responsive to the stock level in said vat in control of said valve means. 7

6. In a paper machine stock flow system for a cylinder machine, a cylinder mold, avat mounting the mold and adaptedto receive stock for forming a paper web on the mold, a flow box, first conduit means flowing stock into said flow box, second conduit means flowing white water into said flow box to dilute the stock therein, third conduit means responsive to the stock level in the flow box flowing stock from the flow box to the vat, draw-off means communicating with the cylinder mold interior withdrawing white water therefrom and communicating with said second conduit means, fourth conduit means responsive to the stock level in the vat communicating with said draw-off means to flow white water into said flow box at a rate sufficient to maintain a constant level in the vat, a flow regulator, a stuff chest flowing stuff into said flow regulator, and fifth conduit means intercommunicating between said draw-off means and said flow regulator to flow white water into said flow regulator, said first conduit means communicating with said flow regulator to receive stock therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 2,609,732 Breyfogle Sept. 9, 1952 FOREIGN PATENTS 677,170 Germany June 20, 1939 

